Manifest Destiny lies beside its essential hubris in the period actioner “Gangster Squad,” but beyond the swaggering idealism seen through eponymous hoodlum Mickey Cohen (played bySean Penn), the film's saturated grab bag of glossy homage proves its final shortcoming. With his third feature, “Zombieland” director Ruben Fleischer frames 1940s Los Angeles — morally compromised, glamorous, and a monument to protect and exploit on both sides of the law — to adapt Paul Lieberman's true-crime articles into cinematic legend, but in lieu of any sharp insight into the period and its notorious figures, the film's brash, ultraviolent encounters instead build a showy exterior with nothing of import left standing.

While these giants of crime and justice still remain, the shadow of Cohen — historically a ruthless NY transplant turned westward — lurks over every frame and exchange in post-WWII LA. His prostitution and drug rings sneak underneath his celebrity, and newspaper ads of Laurel and Hardy pale in comparison to headlines of his exploits or the beauty on his arm, Grace Faraday (Emma Stone). The corrupt police department is benign as well, except for one central higher-up: “Whiskey Bill” Parker (Nick Nolte, one gargle away here from white noise), the LAPD chief who enlists family man and reckless cop John O'Mara (Josh Brolin) to lead a guerilla force into Cohen's operations and destroy them.

The task of deadly provocation proves harder for O'Mara than imagined though, as the most-qualified cops still remain on Cohen's payroll, but — in what appears after “Hitchcock” the second recent tweak of factual marriage — his wife Connie (Mireille Enos) suggests to him an unconventional route. She advises the stubborn, bitter and flawed get their day, and O'Mara sets out to find his new gallery of misfits: the slippery womanizer Jerry Wooters (Gosling) involved with Grace himself, technological mastermind Keeler (Giovanni Ribisi), beat cop Coleman Harris (Anthony Mackie), and a gunslinger (Robert Patrick) alongside his apprentice (Michael Pena).

There is an engaging pleasure to these sequences, as the gang is slowly rounded up from their disparate environments, but stemming back to Enos' clear-headed dynamic, it marks the film's first miscalculation, and one that repeats later on: her character, if fabricated, is ludicrously portrayed, and if an accurate representation, her talents with classified information should've garnered her an LAPD job immediately. Such are the uneven proceedings though. As the newly-assembled squad delves into Cohen's organized crime ring with a vengeance, Fleischer stages a series of escalating showdowns and gunfights, but forgets the more intriguing breaches of morality happening behind the scenes from these lawmen. Ribisi is carved out as the lone voice of dissent — urging Brolin away from the increasingly dangerous activities and back to their families — but one can feel his well-acted quarrels simply biding time until the next unapologetic bloodbath.

Impulsive and steely-faced, Brolin comes off the best here, perhaps because he has the least amount of dialogue in screenwriter Will Beall's fiercely staid script. It's unclear whether Fleischer was going for homage or caricature, but paired with the lingo-heavy dialogue and scattered tonal consistency, he lets down both his narrative and his trusting actors in making their characters more than cops-and-robbers affectations. It is no coincidence that Gosling and Stone are matched here yet again; their “Crazy Stupid Love” chemistry is on full recall in their heated affair, but so is a playfully self-referential tone that leaves them nearly rolling their eyes at the pulpy material, while Patrick, Pena, and Mackie — left to expository and comic relief roles — perform those duties admirably.

Left to carry the wild-eyed dedication then is Penn, absolutely rampant in his prosthetic-led version of Cohen. The mold of bombast he exhibits has no variation though; the promise of menace, once seen in its two settings — bubbly-pissed or violent-pissed, unravels any threat even as he rains death upon half the cast and supporting players. That same process applies to the action sequences as well, which vary in setting and goals but rarely present any kind of surface-level stakes or risk; not until a supporting character (and exactly the one you'd predict) dies in the film's second half does any sense of danger or loss enter the proceedings. The moment is brief, and as the film then charges ahead into its monotonous showdown finale, Fleischer shows where his emotional instincts lie as well.

While those reflexes may collect a certain dreariness to the narrative, the film's aesthetic saves it somewhat. Capturing a digitally-shot LA that looks like streets from “Blade Runner” garnished in period décor, Maher Ahmad's production design strikes a mix of gaudy beauty and uncomfortable attraction, much like the city itself. Together with Mary Zophres' costumes, they represent the most impressive aspect of the picture, but while the popular depiction in film recently has been to minimize, to negate glorification from entering the gangster life, in “Gangster Squad,” Fleischer's lustrous cacophony of violence and posturing makes that vacuous quality apparent enough already. [D]